1. Field of the Invention
This invention relates to electrochemical and electrophysical machining, and more particularly to an apparatus for electrochemical machining of workpieces.
The proposed invention can be used with success for machining elongated workpieces of different cross sectional shape (such as rods, wires, saw blades, shaped rolled products), as well as for polishing the surfaces of workpieces of intricate spatial configuration (such as tableware, electric razors, dentures).
2. Description of the Related Invention
There is known a plasma gun for continuously treating a rolled product designed in the USSR and comprising a bath for heating the workpiece under a layer of electrolyte, side walls of the bath having ports with seals to prevent leaks of the electrolyte, a mechanical current supply contact, a pipe for feeding electrolyte to the bath to be heated, and a pipe for discharging the electrolyte. The housing of the bath functions as the anode, whereas the workpiece functions as the cathode.
However, construction of this known plasma gun fails to ensure a laminar flow of electrolyte in the zone of machining the workpiece. Lack of the laminar character of the flow of electrolyte causes separation of a vaporgas blanket from the workpiece to result in insufficiently high quality of the machined surface. The use in this apparatus of a mechanical current supply contact results at high voltages of, for example, 250-300 V in burns at the surface of the moving workpiece. In addition, this known apparatus fails to ensure selective treatment of the workpiece surface due to a failure to vary the intensity of treatment at different surface portions of elongated workpieces.
Another disadvantage of the above prior art apparatus is failure to provide uniform treatment of the workpiece due to lack of rotation of the workpiece about its longitudinal axis as it moves through the bath for heating.
There is also known an apparatus for electropolishing stainless steel workpieces (cf., GB, A, 1,557,017) comprising a bath accommodating electrodes, means for conveying workpieces to the bath with workpiece grips and a bath for cleaning the electrolyte. The means for conveying the workpiece to the bath includes a conveyer which grips and carries cartridge-enclosed workpieces after stamping and shaping operations. The cartridges have arcuate step elements and plate contacts with the workpieces clamped between these contacts. The cartridges are moved by the conveyer to be successively immersed in the bath. As the cartridges move lengthwise of the bath, the workpieces are electropolished in a solution of orthophosphoric and sulphuric acids. The bath is made of an acid --resistant material, such as polyethylene. Provided at two sides of the moving cartridges are cathode plates imparting to the electrolyte a negative potential. In the course of movement in the bath the cartridges are brought in contact with anode rods imparting to the workpiece a positive potential. After polishing, the workpieces are removed from the bath to be conveyed to a successive bath to be passivated in a solution of nitric acid. Subsequent to passivation, the cartridges with workpieces are conveyed to a washing device where the workpieces are washed in cold and hot water. Then the workpieces are removed from the cartridges, and new workpieces to be treated are loaded into the cartridges.
In this known apparatus the bath fails to provide an ascending laminar flow due to the lack of means for pumping the electrolyte through the treatment zone, which results in low quality of workpiece processing.
The cathode plates are fixed, and therefore during the treatment of workpieces of intricate spatial configuration the density of current in the electrolyte at different surface portions of the workpiece is distributed non-uniformly.
In addition, immersion in the electrolyte of arcuate stops and plate contacts accelerates their premature dissolution and disintegration.
The horizontal positioning of workpieces in the bulky cartridges promotes shielding of the workpieces by the structural elements of the cartridge and prevents uniform treatment of the workpieces by an ascending flow of electrolyte. Further, each workpiece is held inside the cartridge at four points to cause additional shielding effect and larger non-treated surface areas.
The ivariable horizontal position of workpieces of intricate spatial configuration during treatment results in non-uniform processing of different surface portions of the workpieces.